The process of atomizing a liquid stream for such purposes as rapid cooling of the liquid (artificial snow making) or enhanced contact of the atomized liquid with another medium, such as a fluidized catalyst, is well known in the art. It would clearly be desirable to provide an improved process and apparatus for atomizing a liquid stream.
A specific example of an atomization process is the atomization of an oil stream in an FCC or coker unit prior to contacting the oil stream with a fluidized catalyst. Typical FCC unit operations are described below.
Fluidized catalytic cracking of heavy petroleum fractions to produce products such as gasoline and heating oils is well known in the art. In fluidized catalytic cracking, heavy petroleum fractions are often preheated prior to contact with hot, fluidized catalyst particles in a riser reactor. The contact time in the riser reactor is generally in the order of a few seconds. The relatively short contact time encourages the production of gasoline and heating oil range hydrocarbons. Longer contact times can result in overcracking to undesirable end products, such as methane and coke. Important aspects of contacting the heavy petroleum fraction with the fluidized catalyst include the atomization of the heavy petroleum fraction and uniform distribution of the atomized heavy petroleum fraction within the fluidized catalyst. Non-uniform distribution of the heavy petroleum fraction in the fluidized catalyst can lead to localized regions of high catalyst-to-oil ratios and overcracking. Also, poor atomization of the heavy petroleum fraction can lead to localized regions of low catalyst-to-oil ratios resulting in wetting of the catalyst which results in increased coke laydown. In addition, if the heavy petroleum fraction is not sufficiently atomized and does not directly contact the fluidized catalyst upon injection into the riser reactor, then thermal cracking can occur instead of catalytic cracking. Thermal cracking can result in the generation of the undesirable end products of methane and coke. Excess coke is undesirable because the process duties of the stripper and regenerator are increased and the coke can be deposited on the surfaces of the equipment involved. It would be clearly desirable to provide a process and apparatus in which an oil feed stream comprising a heavy petroleum fraction is sufficiently atomized and uniformly distributed within a fluidized catalyst in a fluidized catalytic cracking process.